Furnaces: Neil Simpson

Reducing the impact of CO2 in furnaces

Neil Simpson presents a summary of his 2022 Furnace Solutions paper. He outlines how many m3/hr of gas it takes to produce a tonne of CO2 and how to justify the investment to reduce both.

Starting with gas laws and the basics of combustion, we will look at the distribution/cost of carbon credits and lessons from the past.

In part two we will look at techniques available today and simple financial models to justify investment in energy reduction and resulting emissions.

From gas supply to stack, it will show how analysers, burners, control logic, training, and everything in between can be justified through CO2 and energy savings in a simple spreadsheet.

Basics of combustions and formation of CO2

According to Rogers and Mayhew: � Molar volume = 22.41 m3/kmol at 1atm and 0°C = 22.41Nm3/kmol � Carbon dioxide [CO2] = 44 kg/kmol � Oxygen [O2] = 32 kg/kmol � => Carbon [C] = 44-32 = 12 kg/kmol According to Rose & Cooper 1977: � Molecular weight of hydrogen H is 1.0079

See Fig 1 for basic combustion (ignoring nitrogen).

For simplicity, assuming natural gas is methane, then if you save 1Nm3, you save 2kgCO2. Assuming CO2 is €100/tonne, if you save 1Nm3/h, it saves close to £1500 of CO2 credits PA plus the gas savings. CH4 + 202

 CO2 + 2H2O 1kmol + 2kmol  1kmol + 2 kmol Molar volume = 3 16 + 2*32 = 80 44 +2*18 = 80 mass balance 22.41 Nm3 CH4 gives 44kg CO2 1 Nm3 CH4 gives 1.96kg CO2 509.3 Nm3 CH4 gives 1 tonne CO2

� Fig 1.Basic combustion (ignoring nitrogen). CH4 = 16kg/kmol O2 = 32kg/kmol CO2 = 44kg/kmol H20 = 18kg/kmol

Top

2 12 46 50 461

0.4% 2.6% 10.0% 10.8% 100.0% Allowance

9900584 21088628 30403257 30847839 39091102 % Uk Share

25.3% 53.9% 77.8% 78.9% 100.0%

Fig 2. Analysis of carbon credits by Mr Simpson of 461 UK sites.�

Carbon Credits

The 2021–2025 UK ETS Allocation is available to download from the UK government website.1

My analysis of the 461 sites (Fig 2) would suggest that the two highest sites have 25% of the CO2 allocation. The top 12 have over 50%, while the top 10% represents 46 sites which have 78%.

Perhaps pure coincidence, but on the 21st of April 2021 the UK government enshrined a new target in law to slash emissions by 78% by 2035.2 It is when you get to the top 50 with 79% that we have first two glass plants. Looking at the 23 glass plants listed, it totals only 2.85% of the CO2 credits.

If you utilise all your credits then you can buy more, however, if you can reduce through energy savings or use of cullet then you can transfer or trade on the open market. At the time of

Continued>>

� Fig 3. Coal gasification was used for O-I’s three-port furnace in Alloa, Scotland, UK glassworks in 1950.

submitting the abstract to the Society of Glass Technology Melting Technical Committee the cost was roughly €100 per tonne of CO2. It is now lower, but the cost of energy is now significantly higher.

When looking at investment, Net Present Value [NPV] and Internal Rate of Return [IRR] should realistically be used on major and long-term capital investments. Payback is typically used for short-term energy savings. To date, including ESOS reports, I have never seen CO2 reduction included in the spreadsheets for payback or NPV. The Furnace Solutions presentation and this article are a first attempt to consider including carbon credits.

Lessons from the past

As someone who only has 30+ years of combustion experience, there are a lot of things which I have seen in the past and have heard of. Looking at the papers at Furnace Solutions in June and the ICG in Berlin in July, I am reminded of the 1990’s when all the industrial gas companies were promoting oxygen in a similar way that hydrogen is today. For decades I have been asked if I can burn hydrogen. Getting hydrogen to burn is not a problem, but making it combust where you need/want it is the skill!

Beatson Clark to this day call their furnace operators “teasers” since one of the skills was to tease the gas from the coal. Most of the historic UK glass plants are close to coal fields since this was the fuel source. Whilst before my time, there was a short film made in 1950 to celebrate the 200th anniversary of O-I continuously making glass bottles in Alloa, Scotland, UK.3 The jubilee furnace had a capacity of 60 tpd and used coal gasification.

Fig 3 shows a “well insulated crown” but is a relative term and probably was well insulated for the 1950’s. The threeport cross-fired furnace was fired with producer gas (produced on site). There is also an image of someone using a disappearing filament pyrometer which was a forerunner of the Cyclops.

According to Rose & Cooper, typical produce coal gas was 50% hydrogen! The balance being methane 35%, carbon monoxide 10% and ethylene 5%. In 1950’s we could fire 50% hydrogen so higher should be possible.

When I started at Laidlaw Drew in 1990, many of the UK glass furnaces were still operating on heavy fuel oil. My first gas burner conversion was at UG Peasley in 1993, which is coincidentally the site of the Glass Futures furnace and next to the Furnace Solutions event. My last oil to gas conversion was in 2019.

The early 1990’s was the time when oxy gas and oxy oil were being developed. Oxy gas is relatively easy but oxy oil requires way more skill and care. When looking at the oil conversion of an EAF Rocket Burner to get a longer flame, we investigated the Laidlaw Drew archives and found the 1967 atomiser design jointly developed with Pilkington. Fig 4 is an Eclipse PF100 oxy oil operating on a fibreglass furnace and the shutter speed assumed (1000/s f16) has captured the sinusoidal/swirl effect of the oil atomiser.

Ironically, biodiesel is seen as a possible route to decarbonisation and so is also a well-developed, but perhaps forgotten, combustion technology from the past. Since submitting the abstract - sadly due to the Russian invasion of Ukraine

Fig 4. Eclipse PF100 oxy oil operating on a � fibreglass furnace.

and resulting energy crisis - many glass companies are realising that their natural gas is not uninterruptible, and several are re-instating oil back-up systems.

Upcoming talks

All these topics are included in my Industrial Combustion Decarbonisation 101.4 which can be run as bespoke. The next series of ½ day online training courses are scheduled for December 19th and repeated Tuesday 20th in afternoon.

Two new oil courses are now included due to recent demand. On Wednesday 21st in the morning it will be the ‘Basics of oil combustion in glass furnaces’. Starting with the differences from natural gas will cover regenerative underport and through-port (conical/flat) and recuperative.

On Thursday 22nd again in morning will be ‘Oxy oil combustion in glass furnaces’. Similarly, this will start with the differences between oxy gas and look at 100% conversion for temporary hot hold vs extended production, conical vs flat flame, with risks and possible mitigation. The course will cover methods developed in 1990’s for enabling regenerator repair and boosting/recovery.

For details of courses (Fig 5) and registration contact scecombustiontraining@gmail.com. �

* Independent Consultant, Simpson Combustion and Energy, Scotland, UK neilsimpsonfsgt@btinternet.com

References:

1. https://www.gov.uk/government/ publications/uk-ets-allocation-table-foroperators-of-installations 2. https://www.gov.uk/government/ news/uk-enshrines-new-target-in-law-toslash-emissions-by-78-by-2035 3. https://www.youtube.com/ watch?v=8DVSaanSlAI

Fig 5. Upcoming talks. �